Optimizing Webhooks to Update Existing Rows in Customer.io

i'm trying to leverage Clay as a intermediary between our database and customer.io. primarily to enrich with unfilled data and also to clean names, etc. The problem is that every time i send a daily webhook, it creates a new row and thus i have duplicate contacts creating tons of rows/enrichments. how can i tell a webhook to update an existing row based on unique identifier rather than creating a new row if it's coming in from a webhook?